Power transmission mechanism



3 jmz Maw a N N J. H. WILSON POWER TRANSMISSION MECHANISM Flled July 18 1944 Feb. 28, 1950 Patented Feb. 28, 1950 UNITED STATES PATENT OFFICE 2,499,287 POWER TRANSMISSION MECHANISM John Hart Wilson, Wichita Falls, Tex.

Application July 18, 1944, Serial No. 545,488

.6 Claims.

This invention relates to power transmission mechanism and particularly to mechanism of this class which includes belts and pulleys for the transmission of torque from a drive shaft to a shaft to be driven.

Numerous power transmission mechanisms of the pulley and belt type have been heretofore designed and suggested and many used with eminent success in factories and in fieldinstallations. Where the power to be transmitted from one shaft to another is very considerable the type of belt transmission which includes a plurality of independent belts is frequently utilized. The advantages of employing a plurality of relatively small belts in lieu of a single large belt are well understood, as are likewise the advan-- tages of using individual driving belts which are substantially V-shaped in cross section, and which enter V-shaped grooves in the driving and driven posts. used. 1 t

Wherever belt drives are employed, however, the problem of belt stretching exists and must be adequately met, all types of flexible endless belts tending to lengthen under continued use. In order to maintain close contact of the belt with each of thepulleys around which it passes an idler is customarily employed, such idler pulley being resiliently urged againstone reach of the belt os that, as looseness occurs it is automatically taken up. Where a multiple V-belt drive is employed there must of necessity be utilized a plurality of idler'pulleys, one idler for each belt, and it is the particular purpose of the present invention to provide a power transmission mechanism of the multiple belt type having a novel and improved idler mechanism for automatically taking up the slack in each individual belt of the drive. Naturally, in a multiple belt drive, it is desirable to maintain the belts close together in immediately adjacent parallel planes in order to minimize the length of the driving pulley and the length of the driven pulley. In accordance with my invention a novel idler pulley supporting mechanism is provided whereby, notwithstanding the i act that the driving belts are spaced apart only very slightly, the individual idler pulleys may freely and independently function without interfering with each other. The improved idler construction permits a compactness of the entire drive which cannot be otherwise obtained.

The novel and improved idler mechanism is also so designed that the resilient means which is associated with each idler-and which-serves to The V-belt drive is very widely yieldingly urge thatidler against the belt with which-it cooperates is so arranged with respect to the idler supporting member that, notwithstanding considerable variation in the position of the idler, the force exerted and tending to advance the idler remains substantially constant. Other novel features and advantages of the invention will become apparent to one skilled in the art. In the accompanying drawings one form of the invention is illustrated by way of example. It will be appreciated that minor changes in the design and arrangement of the component elements of the invention may be made, without involving departure therefrom.

In the drawings: I

Figure 1 shows in side elevation, rather diagrammatically, a multiple belt drive having the improved idler mechanism incorporated therein;

Figure 2 is a generaly similar view but showing only the idler mechanism;

Figure 3 is a section on line 3-3 of Figure 2;

Figure 4 is a section on line 4-4 of Figure 1;

and

Figure 5 is a diagram primarily intended to show that an idler advancing spring remains substantially unchanged in length even though the associated idler is advanced substantially as the belt which it engages recedes.

The improved power transmission mechanism may be employed in association with any type of machine and has been found particularly useful in the transmission of power from. a drive shaft suchv as indicated at H! to the driven shaft I l of a pump or the like, portion of the casing of a pump drive being indicated in dotted lines at l2 in Figure 1. Such a power transmission mechanism may include any number of belts and, as indicated in Figure 4, the pulley l3 fixed on drive shaft I0 is provided with three belt-receiving portions, to be engaged by the three belts I l, l5 and I6, respectively, each belt being preferably formed with two V-shaped pulley-engaging portions which are adapted to closely engage correspondingly shaped grooves formed in the pulley. Naturally the surface of pulley l1 fixed upon driven shaft II, is similarly formed. The belts I l, l5 and I6 are closely spaced as clearly apparent in Figure 4, which is desirable, and the idler pulleys, which are indicated at I8, is and 20, respectively, must, if they are positioned adjacent each other, be quite closely spaced.

It is desirable to support the several idlers upon the same frame, generally indicated at 2 I, which supports the drive shaft Ill and to have them disposedin side-by-side relationship. The. idler mounting means contemplated by the invention permits this arrangement. It will be observed that each idler is mounted upon an axle, the several axles being indicated at 22, 23 and 24, respectively. The several idler supporting axles are carried by levers all three of which are mounted for rocking movement upon a single supportin shaft indicated at 25. Each of these levers is of the simple type, being pivotally supported upon shaft 25 intermediate its ends, and the. axle supporting arms of two of them, i. e., levers 26 and 21, are substantially straight, extending radially from shaft 25, with bifurcated outer ends the spaced elements of which are on opposi esidesiof the associated pulleys. Arm 26, for instance, includes a short section 26a the inner end 'of which is integral with or attached to the bearing portion 2612 which encircles shaft 25. To the outer end of section 26a of the lever arm 26 are rigidly secured, as by means of bolts 23 two generally parallel members 260 whichare .likewise disposedradially of shaft 2.5 and' extend outwardly .on oppositesides of idler l8 topoints .in advanceof the axle 2-2, members 260 being provided with aligned sapertures for the reception of the axle.

..Any suitable :type of bearing 'such :as 'theball bearing indicated at .30 may encircle the axle intermediate the members "260 to facilitate free rotationlof the'idler'pulley 1.8. .The 'idler pulley has a relatively wide felly'orxrim 18a to :contact the belt against which it :is to "continuallybear and is also necessarily provided'wit'h side guards or flanges ISb'to p-reventlateral displacement of the associated belt. 'Wheremembers 26-'pass the rim or felly portion l8a of the :idler *each'must be laterally deflected to provide the necessary clearance,.theselateral deflections being indicated at' 26d in Figure 3. .Eachxi'dler -pulleyisupporting arm.'26.must, therefore, berelatively wide, atv least at one point along its length,iii.:.e.,'where'its bifurcations pass around .the:.felly;of :the associated idler "pulley,"and it is1notpossible .to greatlyreduce the width of the supporting arm at this point.

For that .reasonithe wider :or thicker portions of the severalidler'supporting armsiare'so positioned with relation to ;each other'as'notto interfere while,at'the samextime, complete. freedom of relative movement of the idlers in parallel planes is permitted. Thus the arm 2'! which supports idler 20 isformed exactlyzastthe'arm 2-6 which supports theidler l 8,but' the .arm :34 #whichsupports intermediate .idler l9:is so shaped .that its Widest portion 34b islocated beyond the peripheriesiofthe'idlers l8 and'ZlL-the bifurcationsit lc of thisarm being rigidly attached, as'by bolts 35 to .thesend of 'a'semicircular curved portion'iille of arm 34'which is rigidorintegral withthe inner radial portiont laof that'a'rmand encircles the rim orielly 'of the pulley l 9, passing'beneath the pulley as shown'in .Figures 1 and 2 in=order that the uppermost'elements of the pulley maymake contact with the'associated belt l5. ;By so designing'the pulley supportingarrns 2612, 221a and 34a oftthe several levers 26, 2?. andiSfil thezidlerpulleys may bedisposed'in close parallel relationship to each 1 other'while at the s ame:,time:retaining;complete :'.freedom :of movement and one "such ildler may .move, .:for instance, .from ;the position ;in which it is shown in full lines-in :EEligure ,1 ate the position "in 'twhich'lit is indicated :in dotted lines in that figure, without interference withceithersgof theiother idlers.

:The several :levers .26,'I.21r.and.r3.4 :also include oppositely sextending ;.arms 526], 21f and 3 H, :respectivcly, andseach.zofithesesarmszterminateszin a downwardly extending flange, these flanges being indicated at 26g, 21g and 349. To each flange is connected, as by means of a bolt 36 with associated nuts 31 fixed on the bolt on opposite sides of the flange, one end of an elongated helical tension spring 38, the opposite end of which is connected to a stationary element 39 which may conveniently be a portion of the frame. The spring 38 extends in a direction generally parallel to thatof the lever immediately .above it and to which-it connected and the lever in turn extends in a direction generally parallel to that "portion of the belt which lies immediately above. ,Angular. movement of the lever, as the associated belt stretches, does not effect substantially this parallel relationship of the spring and lever, as

maybe seen .frornan inspection of Figure 5 in which a lever is shown in difierent angular posi- '.tions, and the downward movement of that end of the lever to which thelspring is connected does not cause materialshortening of .the spring. Any decrease in tension of the :spring resulting .irom decrease :in its length ;as the lever moves in :a counterclockwise direction (Figure 5), :is .compensated for by increase in thedistance between the spring and shaft 25, i. e., as'the spring tension decreases its lever arm increases. -Hence a;substantially constant force is 'exertedconeach belt by the associated idler. Thetension in;the spring may, of course, be regulated by modifying {the position of the bolt 36, adjustment being :easily efiected by manipulating thenuts 3-1.

.The'invention is in nowise limitedto a power transmission mechanism utilizing any certain number of driving belts. .An idler supportedfin the manner described will be found to,be.eminent- 1y useful where only one'driving belt is employed or theremay bea considerablenumber ofibelts, nine or veleveniforinstance, .inwhich event .the invention will be particularly helpful in thatit permits the belts to be placed as close to .each other as'may be from the standpoint ofdesign of the .driving.and driven pulleys. Minor changes may .be .made in thedesign without departure from the .invention.

Having 1 thus described the invention, what ;is claimed as .new and desired .to be :secured by Letters Patentis:

1. A power transmissionmechanism comprising a plurality of idler,pulleys'disposed in parallel planes each such ,Pulleyghaving a relatively wide .rim and the v:adjacentedges of ,the rimspof adjacent pulleys being disposed in-closelyspaced parallel planes, an axle upon which each :pulley is rotatably supported, each axle being laterally offset from adjacent axles, and a'supporting-arm for each axle, eachsuch arm extending outwardly from the associated axle in such direction as to pass the rim of the-associated pulley at a point where'thatrim is outwardly ofisetfrom adjacent rims.

,2. Apower transmission mechanism comprisingin combination a,plurality of pulleys disposed in parallel planes and so that ran.v arc. of @the rim of .each is offset outwardly :with respectto the rims .of adjacent pulleys, "an axle :associated:with each pulley :and .upon which the pulley iis rotatably amounted, and :an axle :supporting 1arm iBX- tending radially outwardly :from .each .axle :and passing therim of the,associatedzpulleyxat, anoint along the outwardlyoffsetarc thereof.

3. The combination set forth in claim :'2 :in which the :rim of aeach-rpulley isrrelatively wide and :the associated :supporting :arm :is laterally 4. The combination set forth in claim 2 in which the several pulley supporting arms are mounted for oscillation about a common axis.

5. A power transmission mechanism comprising a plurality of driving pulleys, a corresponding number of driven pulleys, a belt connecting each driving pulley to a driven pulley, an idler for each belt, means supporting the idlers, said means including an axle for each idler and upon which that idler is supported, an arm for each axle and upon which that axle is mounted, said arms being mounted for pivotal movement about a common axis, and supporting adjacent axles at diflerent distances from said axis, an intermediate portion of each arm being laterally deflected so as to extend around the rim or folly of the pulley supported thereon, the laterally deflected portions of adjacent arms being ofiset with respect to each other so as not to interfere when said pulleys move relatively to each other.

6. In a power transmission mechanism, the combination with driving and driven pulleys and a flexible endless belt operatively connecting said pulleys, of an idler and means for causing said idler to bear against one reach of said belt at all times, said means including a lever disposed in substantial parallelism to the idler engaged reach of the belt, means supporting the lever for rocking movement about an axis intermediate its ends and closely adjacent said idler engaged reach of'the belt, the arms of the lever extending in substantially opposite directions from said axis, said idler being rotatably supported upon said 6 lever at one end thereof, a spring disposed closely adjacent to and in substantial parallelism to said lever and that reach of the belt which is engaged by the idler, a stationary spring abutment to which one end of said spring is secured, and means connecting the other end of the spring to that end of the lever which is remote from the idler to support such other end of the spring in ofiset relationship to a line passing through the axis about which the lever rocks and the axis about which the idler rotates, so that the tension in the spring will decrease and the moment arm of the spring will increase as the belt yields and the idler advances to maintain the pressure of the idler against'the belt substantially constant for all positions of the idler.

JOHN HART WILSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Germany Nov. 8, 1911 

